This invention relates to mine equipment and in particular to an element to form a rack, a rack made up from such elements and a haulage system for a mining machine which is adapted to traverse to and fro along a mineral face by engaging such a rack.
So-called "chainless" haulage systems have now been in operation, particularly in the course of coal mining, for several years, and various constructions of rack have been proposed, for engagement by the teeth of a drive or haulage device e.g. sprocket or a recirculating chain, all with differing advantages and disadvantages. Thus, one system uses a round link chain which is captivated by suitable furnishings attached to the associated conveyor, whereby should chain breakage occur, injury to personnel in the vicinity of the breakage is avoided. Clearly, chain loading limits are finite, and in mining conditions, with jamming the machine or its cutting head not infrequent, chain overload occurs and when breakage occurs, the chain, of several tons weight, must be pulled from its captivation furnishings, e.g. by being towed by a free-steer vehicle, and a fresh chain transported from an underground store or the surface, and inserted. During the whole of this time, no mineral production can occur. Also, the geometry is such that instead of, ideally, generating only horizontal haulage forces, upward forces are also generated providing no haulage effect and, on the contrary, tending to lift or separate the machine from the conveyor so that trapping slide shoes are required to resist this, but such shoes increase friction and wear. The trend of mining machine manufacturers is to build even more powerful machines producing even higher haulage forces.